Anisotropic non-linear optical response of nodal loop materials

TL;DR

This paper explores the anisotropic non-linear optical responses of nodal loop semimetals, emphasizing how their complex topologies and geometries influence their optical properties, with implications for various materials with multiple nodal lines.

Contribution

It introduces a geometric framework to understand the interplay of topology, geometry, and non-linear optical response in nodal loop semimetals, applicable to a broad class of such materials.

Findings

Response anisotropy depends on nodal loop configuration.

Topological linking affects non-linear optical behavior.

Model applicable to multiple nodal line scenarios.

Abstract

Nodal line semimetals have lately aroused much experimental and theoretical interest, with their gap closing along unconventional trajectories in the 3D Brillouin zone. These trajectories or nodal lines can close into loops and trace out intricate knotted or linked configurations with complicated topologies. In this work, we investigate the semi-classical optical response of two nodal loops in linked, unlinked and touching configurations, focusing particularly on the interplay of response anisotropy and non-linearity. We provide a geometric picture that unifies these aspects and sheds light on the effects of nodal topology and geometry. Based on a model abstracted from generic multi nodal loop scenarios, both with or without linkages, our findings will be applicable for a large class of nodal semimetal materials with multiple nodal lines or loops.